The application covers the creation of a colorless and transparent mesh optical network, where we define colorless to mean no fiber or component is pre-assigned a specific operating channel wavelength and where we define transparent to mean no node of the network becomes blocking for any subset of the operating channel wavelengths passing through to other nodes or being added/dropped from/to a specific colorless (tunable) transponder. Three forms of blocking are explicitly considered: (1) Contention where a channel wavelength is already in use between two or more nodes and thus preventing a distant node from using that channel wavelength to send a signal through those two or more nodes when no optical-to-electrical-to-optical (OEO) conversion is employed at the intermediate nodes. (2) Unpopulated equipment where a channel wavelength is blocked either from passing through or being added/dropped because the equipment is not installed to support that channel wavelength, which is a problem of downward scalability while maintaining all channel wavelengths. (3) Transponders tied to a particular network port preventing signals being added/dropped at any wavelength to/from any other port of the network. It is the second and third definition of blocking we are primarily trying to solve; however, we do solve the first definition of blocking when solving the second and third. Such solutions to the problem of blocking thus provide the desired network transparency.
In regards to the second definition, mesh optical networks can be based on N×N space-switch matrices. Transparency is lost when the equipment is not fully populated at each node, so that certain channel wavelengths are not supported, which is called channel blocking. N×N switches must be installed for each channel wavelength to avoid blocking regardless of the degree of the network at that node.
In regards to the third definition, mesh optical networks can be based on interconnecting “East-West” Reconfigurable Optical Add/Drop Multiplexers (ROADMs) when based on Wavelength Selective Switch (WSS) modules. It is the means of doing adds/drops with “East-West” ROADMs that causes transparency to be lost. For a direct application of “East-West” ROADMs to form degree-2 network nodes in a ring network topology, this lack of transparency has been acceptable owing to the bi-directional nature of rings. When scaling beyond a degree-2 network node to form a mesh network, this lack of transparency is problematic. Alternative routes through the network are not always available and if available their use can exasperate wavelength contention (i.e., the first definition of blocking given above).